Here's one showing how Useful, Usable, and Beautiful together create the conditions for User Delight. Over the years I've been involved in many discussions that throw around these terms but nothing had resolved their relationship to each other in a way that fully made sense to me, so I came up with this.

The conditions needed to deliver a delightful user experience: usable, useful, and beautiful.

These terms are commonly used throughout the UX disciplines:

Useful: It fulfills a user need.

Usable: It is easy to use.

Beautiful: It is aesthetically and emotionally pleasing.

Together they create the conditions that enable delightful user experiences. You really need all three.

Usable plus beautiful without useful is frivolous.

Beautiful plus useful without usable is frustrating.

Useful plus usable without beauty is functional.

It is really much harder than people think to truly delight their users. It often requires teams of UX people with complementary skills and expertise to cover all the bases: design researchers, ethnographers, information architects, interaction designers, usability engineers, visual/graphic designers, motion designers, etc. In an organization that is trying to deliver a product or service, the relationships between Business, Experience, and Technology (BXT) need to be mutually respectful. The focus has to be on user delight. Leadership has to empower and enable it. Culture has to live it. It's difficult to do one of these well, never mind all of them.

The great part is that there has never been a better time to be in UX. Just because it's hard doesn't mean it's not worth the attempt of doing it well.